We have 1 warehouse that fulfils and delivers all pickup orders to our 8 retail locations.
Our retail locations keep 0 inventory/ sock of any and all product.
How do I make an item that only has 5 left in stock at the warehouse available to be purchased and picked up at all 8 retail locations when checking out?
If you want to set your retail stores as an available pickup location at the Shopify checkout; the following box must be checked off for EACH of those locations.
(found at: admin/settings/locations)
However, the next problem you will have is no one will be able to order any items from these locations unless each of these locations has physical inventory in stock.
If you want to have multiple local pickup locations in Shopify they each have to have their own inventory stocked per location. There is no way around this that I am aware of.
It's a platform limitation. Shopify will not let you select multiple local pickup locations for a single location's inventory.